Preparation of dimethylfurane



Patented Nov. 9, 1937 UNITED STATES PATENT OFFICE PREPARATION OF DIMETHYLFURANE No Drawing. Application March 28, 1935, Serial No. 13,482

4 Claims.

The invention relates to a process for preparing 2,5-dimethylfurane. This compound is a liquid, Water-White when pure, having a characteristic odor, and a boiling point of about 93 C. It may be represented by the structural formula CHa.C (lIhCHs CHCH Among the uses to which it is adapted are those of a solvent material, as a reagent in chemical synthesis, or as a reactant for other purposes in the chemical industry. Although the prior art has recognized and identified this compound, it has heretofore been detected only in very small quantities, usually as a by-product in the preparation of other materials. Of its formation synthetically, very little, if anything, appears to have been known prior to this invention.

We have found that 2,5-dimethylfurane is obtainable from the pyrolysis of acetone, and can be isolated from the products of such a reaction, under proper control of heating and quenching conditions. The formation of dimethylfurane is promoted by a short period of contact to a high reaction temperature, and a very rapid quenching of the gases issuing from the reaction chamber.

The pyrolysis may be conducted in a usual type of acetone cracking unit, in which preheated acetone vapors are led through a heated tube or chamber at a velocity which may be varied to control the time of reaction desired. Normally, the reaction period, or the time that the average gas molecule is subjected to the cracking temperature, is but a fraction of a second, varying, for example, in known processes, from about 0.15 to 0.5 second. For the purpose of the present invention, this reaction period should not exceed 0.15 second, and a gas velocity sufiicient to subject it to a pyrolyzing temperature for less than 0.1 second is preferred and most effective.

The maximum temperature reached in the cracking zone must also be closely controlled, so that the outlet gas temperature is about 710 C. or higher. Tests made at temperatures below 700 C. show no indication of the formation of 2,5-dimethylfurane. A very rapid, or immediate, quenching of the cracked gases is also essential, and the elapsed time of passage from the zone of maximum cracking temperature to contact with a suitable quenching medium should not be substantially greater than .01, second.

Cooling may be effected with a stream of liquid at a temperature of about 30 C. in the usual type of quenching tower.

A mixture of reaction products is obtained from this pyrolysis, including, in addition to the one sought by this invention, others such as ketone and methylethyl ketone. From this mixture, 2,5-dimethylfurane, boiling at a temperature of about 93 C., may be readily isolated in pure form, by means of fractional distillation.

It will be understood that the novelty of this invention resides primarily in conducting an acetone pyrolysis in such a manner as to favor the formation of 2,5-dimethylfurane. This is effectively accomplished under the conditions given for a minimum cracking temperature, as well as a maximum reaction and quenching time, but higher temperatures and a reduction in the effective time elements mentioned, may be desirable, the latter of which can be readily accomplished by an increase in the gas and cooling liquid velocities. Modifications in this respect are intended to be included within the scope of the appended claims.

We claim:

1. A process which comprises pyrolyzing acetone at a temperature above 700 C. for a period not greater than about 0.15 second, immediately cooling the reaction gases in a liquid medium, and isolating 2,5-dimethylfuranefrom the resulting liquid mixture.

2. A process which comprises pyrolyzing acetone at a temperature above 700 C. for a period not greaterthan about 0.15 second, immediately contacting the reaction gases with a liquid cooling medium within a period not greater than about 0.10 second, and isolating 2,5-dimethylfurane from the resulting liquid mixture.

3. A process which comprises pyrolyzing acetone at a temperature above 700 C. for a period less than 0.10 second, contacting the reaction gases within a period not greater than 0.10 second with a liquid cooling medium at a temperature of about 30 C., and isolating 2,5-dimethylfurane from the resulting liquid mixture.

4. A process which comprises pyrolyzing acetone at a temperature above 700 C. for a period less than 0.10 second, contacting the reaction gases Within a period of about 0.01 second with a liquid cooling medium at a temperature of about 30 C., and isolating 2,5-dimethylfurane by fractional distillation from the resulting liquid mixture.

GRANVILLE A. PERKINS. WALTER J. TOUSSAINT.

, CERTIFICATE OF CORRECTION. Patent No, 2,098,592 November 9,'- 1957,

GRANVILIE A. PERKINS, ET AL,

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Second collimn, line 6-7, for the word ketone first occurrence, read ketene; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office,

Signed and sealed this 25th day of Jamar- A. Do 1958.

Henry- Van Arsdale,

(Seal) Acting -qoxrm liseioner of Patents 

